Orchid Fleck Virus: Brevipalpus californicus Mite Transmission, Biological Properties and Genome Structure

Abstract

Orchid fleck virus (OFV) causes necrotic or chlorotic ring spots and fleck symptoms in many orchid species world-wide. The virus has non-enveloped, bacilliform particles of about 40 nm x 100-150 nm and is sap-transmissible to several plant species. OFV is transmitted by the mite Brevipalpus californicus (Banks) in a persistent manner and efficiently transmitted by both adults and nymphs, but not by larvae. Viruliferous mites retain their infectivity for 3 weeks on a virus-immune host. The genome of OFV consists of two molecules of 6431 (RNA1) and 6001 nucleotides (RNA2). The RNAs have conserved and complementary terminal sequences. RNA1 contains five open reading frames (ORF), and RNA2 encodes a single ORF. Although some of the encoded proteins of OFV have sequences similar to those of proteins of plant rhabdoviruses, OFV differs from viruses in the family Rhabdoviridae in having a bipartite genome.

Chlorotic spots on Clerodendrum, a disease caused by a nuclear type of Brevipalpus (Acari:Tenuipalpidae) transmitted virus

“…This fact strongly suggests that the virus multiplies in the mite, thus B. phoenicis/ClCSV relationship is of the circulative/propagative type. This is in agreement with the conclusions reached in the transmission of OFV by B. californicus (Kondo et al, 2003).…”

“…Examination of thin sections of the tissues from the lesions of experimental or naturally ClCSV-infected plants appeared similar to those reported for other nuclear types of BTrV as OFV and CoRSV Kondo et al, 2003;Chagas et al, 2003). Typical electron lucent viroplasm in the nucleus and short rod shaped particles were seen mostly in mesophyl parenchyma cells, and rarely in vascular parenchyma.…”

“…Its genome is divided in two pieces of about 6 kb with gene organization similar to that of Rhabdoviruses. A new genus Dichorhabdovirus has been proposed for OFV (Kondo et al, 2006), of which CoRSV and ClCSV will be possible members. As soon as more informa-Sci.…”

“…2006b). The only exception is OFV which has been found worldwide in orchids (Kondo et al, 2003). This study presents a detailed description of the transmission and host range of a new species of a nuclear type of BTrV isolated from the chlorotic spots on leaves of C. x speciosum, which is tentatively named Clerodendrum chlorotic spot virus (ClCSV).…”

IPM Potentials of Microbial Pathogens and Diseases of Mites

“…(Van Dijk & Van der Vlugt, 1994) and Brevipalpus spp. are known as vector of, among others, citrus leprosis virus in citrus in Latin America (Rodrigues, Kitajima, Childers, & Chagas, 2003), of orchid fleck virus in many orchid species world-wide (Kondo, Maeda, & Tamada, 2003) and of coffee ringspot virus in coffee in Brazil and Costa Rica . It is doubtful whether these vector mites suffer from the presence of viruses inside their body, although the high plain virus and Pigeon Pea Mosaic virus seem to replicate in their respective vectors (Kumar, Duncan, Robert, Jones, & Reddy, 2002).…”